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      <title>MySQL相关面试题 - 交互式测验</title>
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    </head>
    <body>
      <div class="main-wrapper">
          <div class="quiz-container">
            <div class="quiz-header">
              <h1>MySQL相关面试题 - 交互式测验</h1>
              <p>检验你对文档内容的理解程度</p>
            </div>
            <div id="quiz-content">
                <div class="quiz-body">
                    <div class="progress-bar">
                        <div id="progress-indicator"></div>
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                    <div id="question-container">
                      <p id="question-text"></p>
                      <ul class="options-list" id="options-list"></ul>
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                    <div id="hint-container" class="hint-container"></div>
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      </div>

      <script>
        const quizData = [
  {
    "question": "根据文档，数据库事务的“隔离性 (Isolation)”特性主要解决了什么问题？",
    "options": [
      "确保事务中的操作要么全部成功，要么全部失败。",
      "保证一个用户的事务在执行时，不会被其他并发执行的事务所干扰。",
      "确保事务一旦提交，其对数据库数据的改变就是永久性的。",
      "保证事务执行前后，数据的完整性约束不被破坏。"
    ],
    "correctAnswerIndex": 1,
    "explanation": "隔离性（Isolation）是指多个用户并发访问数据库时，一个用户的事务不应该被其他用户的事务所干扰。文档中明确指出，多个并发事务之间的数据要相互隔离，以避免如脏读、不可重复读等问题。",
    "source": "文档中「讲一下数据库的ACID」部分",
    "hint": "思考一下，在多用户同时操作数据库的环境下，为了防止数据混乱，事务之间需要建立什么样的“墙”？"
  },
  {
    "question": "文档中提到了MySQL支持的四种事务隔离级别。请问，MySQL默认的隔离级别是什么？",
    "options": [
      "读未提交 (READ UNCOMMITTED)",
      "串行化 (SERIALIZABLE)",
      "可重复读 (REPEATABLE READ)",
      "读提交 (READ COMMITTED)"
    ],
    "correctAnswerIndex": 2,
    "explanation": "文档中明确指出，SQL标准定义了四种隔离级别，并强调“可重复读（REPEATABLE READ）是 MySQL 的默认级别”。这个级别可以防止脏读和不可重复读，但仍可能出现幻读。",
    "source": "文档中「事务的隔离级别」部分",
    "hint": "在性能和隔离强度之间，MySQL选择了一个折中的默认方案。"
  },
  {
    "question": "在数据库分库分表策略中，“hash取模”策略是如何决定数据应该存放在哪个表中的？",
    "options": [
      "根据数据插入的时间范围（如按年、按月）来分配表。",
      "根据指定的路由键（如 user_id）对分表总数进行取模运算，按结果分配到对应的表。",
      "将所有数据随机分配到不同的表中以实现负载均衡。",
      "总是将新数据插入到当前数据量最小的表中。"
    ],
    "correctAnswerIndex": 1,
    "explanation": "“hash取模”策略的核心是确定性地将数据分散到各个表中。文档中描述，该策略通过对一个指定的路由key（通常是user_id或订单id）与分表总数进行取模运算，得到的余数就决定了数据应该存放在哪一张表中。",
    "source": "文档中「分库分表后是怎么把数据存到数据库中的」下的「hash取模」部分",
    "hint": "文档中举了一个例子：id=3，对4取模，就会得到3，数据就放到t_order_3。"
  },
  {
    "question": "在MySQL主从复制的机制中，从服务器（slave）上的“SQL线程”主要负责什么任务？",
    "options": [
      "从主服务器（master）请求binlog事件并将其写入本地的中继日志。",
      "读取中继日志（relay log）中的内容，并在从服务器上重放执行，以实现数据同步。",
      "记录主服务器上的所有数据更改到二进制日志（binlog）。",
      "监控主服务器的状态，并在主服务器宕机时自动进行故障转移。"
    ],
    "correctAnswerIndex": 1,
    "explanation": "文档中详细描述了主从复制的过程。从服务器上有两个关键线程：I/O线程和SQL线程。其中，I/O线程负责从主库读取binlog并写入中继日志（relay log），而SQL线程则负责读取中继日志并执行其中的SQL语句，从而将更改应用到从库。",
    "source": "文档中「mysql集群如何实现消息同步」部分",
    "hint": "主从复制分为两步：拉取数据和应用数据。SQL线程负责的是哪一步？"
  },
  {
    "question": "根据文档中提到的索引创建原则，以下哪种情况最不适合为字段创建索引？",
    "options": [
      "字段经常被用作查询条件（WHERE子句）。",
      "字段是外键，经常用于表连接（JOIN）。",
      "字段的更新操作（UPDATE）非常频繁。",
      "字段经常用于数据排序（ORDER BY子句）。"
    ],
    "correctAnswerIndex": 2,
    "explanation": "虽然索引能极大地提高查询速度，但它也会带来维护成本。每次对索引字段进行增、删、改操作时，数据库都需要更新索引结构。因此，文档明确指出，“更新频繁的字段不建议设置索引”，以避免索引维护带来的性能开销。",
    "source": "文档中「开发过程中索引创建的原则？」部分",
    "hint": "思考一下索引的代价。除了占用磁盘空间，索引在什么操作下会产生额外的开销？"
  },
  {
    "question": "根据文档描述，在什么情况下本地事务会失效，从而需要引入分布式事务？",
    "options": [
      "当单个数据库的并发连接数过高时。",
      "当需要对单张大表进行批量插入操作时。",
      "当系统架构涉及分库分表或操作多个数据源时。",
      "当MySQL主从复制出现严重延迟时。"
    ],
    "correctAnswerIndex": 2,
    "explanation": "文档中明确指出：“在分库分表的和分布式的情况下本地事务就会失效”以及“多数据源的情况下本地事务会失效”。这是因为本地事务只能保证单个数据库内操作的原子性，一旦一个业务操作需要跨越多个数据库，就需要分布式事务来协调，以保证所有操作要么都成功，要么都失败。",
    "source": "文档中「分布式事务，谈一谈你对分布式事务的了解」和「你用MySQL的话，有用主从吗...」部分",
    "hint": "本地事务的作用范围是有限的。当一个业务操作超出了这个范围时，就需要更高级的事务机制了。"
  },
  {
    "question": "文档对比了 `char` 和 `varchar` 两种数据类型，它们在存储机制上的核心区别是什么？",
    "options": [
      "`char` 的查询效率总是高于 `varchar`。",
      "`char` 是固定长度存储，而 `varchar` 是可变长度存储。",
      "`char` 只能存储字母和数字，而 `varchar` 可以存储任意字符。",
      "只有 `varchar` 类型的字段才能创建索引。"
    ],
    "correctAnswerIndex": 1,
    "explanation": "文档中清晰地解释了两者最大的不同在于长度是否固定。`char(10)` 无论存入多少字符，都会占用10个字节的空间。而 `varchar(10)` 存入'abc'三个字符时，实际占用的空间是3个字节外加1-2个用于记录长度的字节。这种特性使得 `varchar` 在存储空间上更具优势，而 `char` 在处理定长数据时效率可能更高。",
    "source": "文档中「mysql char和varchar的不同？」部分",
    "hint": "一个像“定制盒子”，大小固定；另一个像“伸缩袋”，大小随内容而变。"
  }
];
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        let score = 0;
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                // 高亮正确答案
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            document.getElementById('quiz-footer').style.display = 'none';

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            const totalQuestions = quizData.length;
            const answeredCount = userAnswers.filter(a => a !== null).length;
            const wrongCount = answeredCount - correctCount;
            const skippedCount = totalQuestions - answeredCount;
            const accuracy = totalQuestions > 0 ? Math.round((correctCount / totalQuestions) * 100) : 0;
            const errorRate = totalQuestions > 0 ? Math.round((wrongCount / totalQuestions) * 100) : 0;

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                '<h2>答题报告</h2>' +
                '<div class="score-summary">' +
                '<div class="score-card">' +
                '<h3>得分</h3>' +
                '<p>' + correctCount + ' / ' + totalQuestions + '</p>' +
                '</div>' +
                '<div class="score-card">' +
                '<h3>正确率</h3>' +
                '<p>' + accuracy + '%</p>' +
                '</div>' +
                '<div class="score-card">' +
                '<h3>错误率</h3>' +
                '<p>' + errorRate + '%</p>' +
                '</div>' +
                '<div class="score-card score-details">' +
                '<table>' +
                '<tr><td>正确</td><td>' + correctCount + '</td></tr>' +
                '<tr><td>错误</td><td>' + wrongCount + '</td></tr>' +
                '<tr><td>未答</td><td>' + skippedCount + '</td></tr>' +
                '</table>' +
                '</div>' +
                '</div>' +
                '<div class="report-actions">' +
                '<button id="review-btn">回顾测验</button>' +
                '<button class="primary" onclick="location.reload()">再试一次</button>' +
                '</div>' +
                '</div>';

            let reportEl = document.querySelector('.final-score-container');
            if (reportEl) {
                reportEl.remove();
            }
            quizContentEl.insertAdjacentHTML('beforeend', finalScoreHtml);
            document.getElementById('review-btn').addEventListener('click', reviewQuiz);
        }

        function reviewQuiz() {
            const reportEl = document.querySelector('.final-score-container');
            if (reportEl) {
                reportEl.remove();
            }

            document.querySelector('.quiz-body').style.display = 'block';
            document.getElementById('quiz-footer').style.display = 'flex';
            
            currentQuestionIndex = 0;
            loadQuestion();
            updateNavigationButtons(); // Ensure nav buttons are correctly displayed
        }

        // Event Delegation for options
        optionsListEl.addEventListener('click', (event) => {
            if (event.target && event.target.matches('li.option-item')) {
                // Check if the question has already been answered
                if (userAnswers[currentQuestionIndex] === null) {
                    const selectedIndex = parseInt(event.target.dataset.index, 10);
                    selectOption(selectedIndex);
                }
            }
        });

        prevBtn.addEventListener('click', goToPreviousQuestion);
        nextBtn.addEventListener('click', goToNextQuestion);
        hintBtn.addEventListener('click', showHint);
        
        // 初始加载
        loadQuestion();
      </script>
    </body>
    </html>
  